A one-piece, integrated control valve means is known (FR-A-82 21663), which reduces risks of damage due to the breaking of an external pipe. It is autoclave, which means that the pressure within the container applies the main valve to its seat.
An integrated control safety valve is also known (DE-A-2315 017), which has a body provided with an intake and an outlet for a fluid. A piston traversed by an axial channel mounted in sliding manner bears on a seat. A control valve is applied to a seat by means of a regulatable helical spring.
The valve means has an auxiliary piston mounted on the main piston and has a very large surface area (three hundred times greater) than that of the piston. The lower face of the piston is connected by a channel to a chamber downstream of the control valve.
The thus defined valve means is autoclave, because the surface of the face of the piston directed towards the closing pressure chamber of the main valve exceeds the surface of the main valve directed towards the enclosure. Thus, in the case of a slow pressure variation within the enclosure, the pressure is imparted to the closing chamber, so that the valve means is autoclave.
However, if the control valve is blocked for any reason, the main valve can no longer open, which would lead to a pressure increase which could lead to the enclosure fracturing.
In the same way, in the case of a sudden increase in the pressure within the enclosure, a certain time lag is necessary due to the small passage cross-section of the channel leading to the opening chamber to enable the pressure in the opening chamber of the main valve to reach an adequate value for bringing about the opening of the main valve. Thus, the enclosure could suffer serious damage before the valve means has been able to fulfil its function--i.e., that of lowering the pressure.